This application claims priority under 35 U.S.C. xc2xa7119 of FR-99/13219, filed Oct. 22, 1999, hereby expressly incorporated by reference.
1. Technical Field of the Invention
The present invention relates to novel water-in-oil (W/O) cosmetic/dermatological emulsions comprising at least one aqueous phase and at least one fatty phase; at least one photoprotective system/agent suited for screening out UV-irradiation, including at least one organic UV-screening agent insoluble in such emulsions, in micronized form or state; and also including at least one nonscreening organomodified silicone.
The present invention also relates to cosmetic/dermatological compositions suited for the photoprotection of the skin or of the hair.
2. Description of the Prior Art
It is known to this art that light radiation of wavelengths of from 280 nm to 400 nm permits tanning of the human epidermis, and that radiation of wavelengths more particularly of from 280 nm to 320 nm, i.e., UV-B radiation, causes erythemas and skin burns which can hinder the development of natural tanning.
For these reasons as well as for aesthetic reasons, there is a constant demand to control this natural tanning such as to thereby control the color of the skin; it is therefore advisable to screen out UV-B radiation.
It is also known to this art that UV-A radiation of wavelengths of from 320 nm to 400 nm, which promotes tanning of the skin, also is capable of causing damage thereto, in particular in the case of a sensitive skin or of a skin continually exposed to solar radiation. UV-A radiation, causes, in particular, loss of elasticity of the skin and the appearance of wrinkles which promotes premature skin aging. UV-A radiation promotes the onset of the erythema reaction or amplifies this reaction in certain individuals and may even be responsible for phototoxic or photoallergic reactions. Thus, for aesthetic and cosmetic reasons such as the preservation of the natural elasticity of the skin for example, an increasing number of individuals seek to control the effect of UV-A radiation on their skin. It is therefore desirable to also screen out UV-A radiation.
A wide variety of cosmetic compositions intended for the photoprotection (UV-A and/or UV-B) of the skin are also known to this art.
These anti-sun or sunscreen compositions are quite often provided in the form of an emulsion, of the oil-in-water (O/W) type (namely, a cosmetically and/or dermatologically acceptable carrier comprising an aqueous dispersing continuous phase and a fatty dispersed discontinuous phase) or of the water-in-oil (W/O) type (dispersed aqueous phase in a continuous fatty phase), which contains, at various concentrations, one or more lipophilic conventional organic UV-screening agents and/or inorganic nanopigments of metal oxides, which are suited for selectively absorbing the harmful UV radiation, these screening agents (and the quantities thereof) being selected according to the desired sun protection factor (the sun protection factor (SPF) being mathematically expressed by the ratio of the irradiation time required to attain the erythematogenic threshold with the UV-screening agent to the time required to attain the erythematogenic threshold in the absence of UV-screening agent). In such emulsions, the hydrophilic screening agents are present in the aqueous phase and the lipophilic screening agents are present in the fatty phase.
The oil-in-water emulsions are, in general, more accepted by the consumer than the water-in-oil emulsions because, in particular, of their pleasant feel (similar to water) and their presentation in the form of a non-oily cream or milk; however, they also more readily lose their UV protection efficacy as soon as they come into contact with water. Indeed, the hydrophilic screening agents tend to disappear in water, upon washing in the sea or in a swimming pool, under the shower or when engaged in water sports; thus, anti-sun or sunscreen compositions containing same, whether alone or combined with lipophilic screening agents, no longer provide the desired initial protection as soon as the substrate (skin or hair) to which they have been applied is contacted with water.
Anti-sun (sunscreen) compositions exhibiting improved resistance to water have been formulated as water-in-oil emulsions. Indeed, a hydrophilic screening agent is more stable to water in a water-in-oil emulsion than in an oil-in-water emulsion. However, as indicated above, such compositions are not yet completely satisfactory since they promote, after application, a fat-like impression which is particularly unpleasant for the user.
Thus, serious need continues to exist for anti-sun or sunscreen compositions which impart to the skin and/or the hair effective solar protection which is stable over time and resistant to water (stability to water) and the cosmetic performance of which presents features that would be comparable to those obtained with conventional oil/water emulsions.
It has now surprisingly and unexpectedly been determined that specific emulsions containing at least one organic UV-screening agent insoluble in micronized form in the different phases of these emulsions and at least one particular non-UV-screening organomodified silicone not only provide anti-sun compositions whose cosmetic performance features are comparable to those generally associated with a conventional sunscreen composition formulated as an oil/water or water/oil emulsion, but also exhibit good stability as well as enhanced stability to water.
These discoveries constitute the basis of the present invention.
Briefly, the present invention features cosmetic/dermatological water-in-oil emulsions comprising:
(a) at least one aqueous phase and
(b) at least one fatty phase;
(c) at least one photoprotective system or agent suited for screening out UV radiation, containing at least one organic UV-screening agent insoluble in such emulsions, in micronized form, in which the mean size of the particles ranges from 0.01 to 2 xcexcm;
(d) at least one non-UV-screening organomodified silicone which comprises oxyalkylenated substituents. Characteristically, said organic UV-screening agent is neither 2,4,6-tris[p-(2xe2x80x2-ethylhexyl-1xe2x80x2-oxycarbonyl)anilino]-1,3,5-triazine in micronized insoluble form nor the compound having the structural formula: 
in micronized insoluble form.